Furnace for burning insulation



Oct. 8, 1968 1.1.. HALL 3,404,875

FURNACE FOR BURNING INSULATION Filed Oct. 14. 1965 4 Sheets-Sheet 1INVENTOR= \SAlAH LEESHALL 13 cum", 52% cmm Oct. 8, l. L. HALL FURNACEFOR BURNING INSULATION Filed Oct. 14. 1965 4 Sheets-Sheet 2 INVENTOR=ISAIAH LEES HALL Oct. 8, 1968 L. HALL FURNACE FOR BURNING INSULATION 4SheetsSheet 5 Filed Oct. 14. 1965 \NVENTOR \SA\AH LEES HALL B CA9,Slam-m1? CGMIBL Oct. 8, 1968 L. HALL 3, 0 ,8 5

FURNACE FOR BURNING INSULATION Filed. Oct. 14. 1965 4 Sheets-$heet 4 TINVENTOR:

\SAIAH LEES HALL B3, CAM,Scvmn{Cm-M United States Patent 3,404,875FURNACE FOR BURNING INSULATION Isaiah Lees Hall, Meeching House, ChurchHill, Newhaven, Sussex, England Filed Oct. 14, 1965, Ser. No. 495,962Claims priority, application Great Britain, Oct. 19, 1964, 42,508/64 1Claim. (Cl. 266-37) ABSTRACT OF THE DISCLOSURE A furnace for burninginsulation off of cables and for the recovery of metal from such cablescomprises a smoke-burning chamber, located above and rearwardly of thehearth with a bridge wall extending upwardly and running transverselyacross the rear of the hearth but terminating below the roof of thehearth to define a flue entrance leading from the hearth to thesmoke-burning chamber. The outlet to the chimney from said smoke burningchamber is located below the top of the bridge wall.

A second smoke-burning chamber may be located downstream in the chimneyand triggered by a photosensitive smoke warning device so as to beoperable only when the smoke density exceeds a predetermined level.

The present invention relates to furnaces and in particular to furnacesof the kind that are, for example, suitable for the burning off ofinsulation from cables and for the running off of lead and reclaimingcopper from such cables.

It is an object of the present invention to provide a furnace of thekind stated that ensures maximum thermal efiiciency and minimum fuelconsumption, as Well as an effective elimination of the smoke producedby the burning off process.

It is a further object of the present invention to provide a basicfurnace structure that is capable of handling rubber covered cable andthat is capable of maintaining the smoke produced therefrom below 50%obscurity (Ringlernann 2), which is the figure set out by the provisionsof the Clean Air Act.

It is a further object of the present invention to provide a basicfurnace as stated plus additional means whereby P.V.C. covered cablescan be burnt off in the furnace and the numerous chemical gasesgenerated by the burning of the P.V.C. can be eliminated. Such gasesinclude Phosgene and HCl.

According to the present invention a furnace for the burning off ofinsulation from cables and for the recovery of metal from such cables,comprises a hearth that slopes downwardly towards the front of thefurnace, a roof and side walls extending along the hearth, one or moreburners associated with said hearth for burning off said insulation, aflue at the upper end of said hearth, said flue being closed at itsupper end to form a smoke burning chamber for collecting gases generatedabove the hearth, one or more burners associated with said smoke burningchamber for burning the gases collecting therein, and an outlet for theburnt gases at or near the lower end of the smoke burning chamber.

With a furnace constructed in this manner all the smoke created abovethe hearth must first pass, preferably over a bridge wall or throughchecker brick, into the smoke burning chamber where it is destroyed bythe burners therein before passing downwardly and outwardly at thebottom of the smoke burning chamber into a smoke stack which thenconveys the destroyed gases away into the atmosphere. The smoke burningchamber is, of

course, of an adequate size to accommodate all of the smoke producedabove the hearth and the burners therein may operate in a mannermaintaining the chamber at approximately 900 C.

To enable the lead and copper of the cables to be recovered the hearthslopes downwardly towards the front of the furnace, said hearth alsohaving a gentle downward slope from each of its two sides towards itscentre so as to form a central gully that terminates at the front of thefurnace in the form of a pouring spout.

The furnace is provided with an arched roof over the hearth and theroof, hearth, and side walls are of brick to ensure a maximum of heatradiation onto the materials being treated on the hearth. Such brickworkpreferably comprises three courses to ensure long life at hightemperatures and the sloping hearth is preferably covered with steelplate to withstand the raking out of the cable.

The exterior of the furnace is preferably sheathed in steel and thewhole is supported by a main framework constructed of heavy steelreinforced to withstand rough usage and the high temperatures involvedin the burning off of various materials in the furnace.

Mounted in each side wall of the furnace, near the front thereof, areoil or gas fired burners of the single lever self-proportioning type toensure correct atmosphere regardless of the smoke or gases produced bythe rubber, P.V.C., etc., which burners are operated in conjunction witha motorised fan. At various points along the side walls of the furnacethere are also a number of forced auxiliary air supply nozzles to ensurean adequate air supply for the burning of the waste materials in thefurnace, these auxiliary air supplies being additional to the air usedfor atomising the fuel oil if fuel oil is used or for supplying thenecessary air for the combustion of the gas if gas firing is used.

Where the furnace is to be used for the burning off of P.V.C. thefurnace is associated with a cooling and a scrubbing plant foreliminating the dangerous gases produced by the burning of P.V.C. beforethe residual gases are released to atmosphere through a stack.

In order that the invention may be clearly understood reference will nowbe made to one particular embodiment thereof as depicteddiagrammatically in the accompanying drawings and in which:

FIGURE 1 is a side elevation, in cross section, of the basic structureof the furnaces;

FIGURE 2 is a view similar to FIGURE 1 but showing the exterior of thefurnaces;

FIGURE 3 is a front elevation of FIGURE 2;

FIGURE 4 shows an optional additional smoke burning chamber associatedwith the smoke stack from the basic furnace; and

FIGURE 5 shows the basic structure supplemented by a gas cooling andscrubbing plant.

Referri g first to FIGURE 1, it will be seen that there is shown incross section a furnace in which a hearth 1 is provided that slopesgently downwardly towards the front of the furnace. As is shown inbroken lines in FIG- URE 3 this hearth also has a gentle downward slopefrom each of its two sides towards its centre so as to form a centralgully that terminates at the front of the furnace in the form of apouring spout 2. This hearth is of brickwork and is reinforced on itsupper surface with steel plate 3 to withstand the raking out of thematerials from the hearth.

Over the hearth 1 is an arched brick roof 4, also made of brick, saidroof 4 being supported by two brick side walls 5. Extending across therear of the hearth 1 is a bridge wall 50 that does not reach the roof 4,the res-ulting opening acting as a flue leading to a smoke burningchamber 10 described hereinafter.

In each of the side walls 5, forwardly of the furnace and spaced abovethe hearth 1 is a burner 6 that is illusrated diagrammatically by arectangle and may be of any suitable form. Preferably, however, eachburner is of the oil or gas fired type and of the single level selfproportioning type to ensure correct atmosphere regardless of the smokethat is present above the hearth. Burners of this type are manufacturedby The Wallsend Slipway & Engineering Company Limited and many otherfirms.

Near the rear of the hearth 1 there is provided in each of the sidewalls an air inlet 7 for supplying air for the burning of the wastematerials on the hearth.

The arched roof 4, at its inner end, rises upwardly in the form of abridge wall 8 and then extends rearwardly again as at 9 to form acovered flue or smoke burning chamber 10, into which the hot smoke andgases from the hearth pass over the bridge wall 50 and collect forburning by two further burners 11, also indicated diagrammatically bysquares there being a burner 11 in each of the side walls supporting thetop 9 of the smoke burning chamber 10. These burners 11 are preferablythe same as the burners 6 and may operate at approximately 900 C., andmaintained at this temperature by automatic control.

The rear of the smoke burning chamber is defined by a wall 12 thatextends downwardly towards a base 13 of the furnace but is spaced fromthe base 13 so as to form an outlet 14 for the burnt gases. In each ofthe side walls of the smoke burning chamber 10, near the base 13, thereis provided an air inlet 15 by means of which the necessary air tosupport the combustion of the burning gases is provided.

The burnt gases escaping via the outlet 14 are led into a chimney 16that extends upwardly past a damper 17 for controlling the rate at whichthe gases are permitted to escape.

The whole of the brickwork is encased externally in steel 18 and issupported by a main framework 19 of steel.

At the front of the furnace there is a door 20 that is verticallydisplaceable by means of suitably counterbalanced hoisting gearindicated generally at 21, the sides of the door sliding in guidingchannels 22 and having door sealing means 23 of any known kind forensuring an accurate hermetic seal when the door is closed and thefurnace is in operation. The door 20 has an inspection hole 24. The door20 is preferably electrically operated and is energised through suitableswitching means such that the motor driving the door is stopped when thedoor is fully raised or fully lowered.

Extending over the door 20 is a cowling 25 for taking away any fumes orsmoke accumulating at the front of the furnace when the door is open,and also to take care of steam and smoke if materials that are beingtreated are quenched in water near the entrance to the furnace.

Mounted above the furnace is a suction fan 26 that extracts all thesmoke, fumes, and air from the cowling 25 via ducting 27 and feeds thismixture back into the furnace via ducting 28 leading to the air inlets 7and 15. Thus, all offensive smoke, fumes, etc., collecting in thecowling 25 are fed back into the furnace to be burnt therein beforeescaping up the chimney 16.

The suction fan 26 is also used to supply air to the burners 6 and 11there being air-feed pipes 29 for this purpose interconnecting thesuction fan 26 and the burners 6, 11.

It will be seen from the above, which is one example only of a basicfurnace according to the present invention, that not only is the smokeproduced above the hearth subjected to considerable combustion but thatany smoke escaping from the hearth must pass upwardly into the smokeburning chamber 10 where it is subjected to further burning by theburners 11 before being permitted to escape downwardly via the outlet 14and into the chimney 16. The furnace is provided with a photo-electricsmoke warning device 52, such a device being positioned at any suitablelocality for example in the chimney 16. Such a device may operate aflashing light and bell to indicate if the furnace is overloaded at anytime and is thereby creating an excess of fumes and smoke at the flueoutlet.

The temperature in the smoke burning chamber 10 is preferably maintainedconstant and to this end the furnace includes a pyrometer temperatureindicator associated with the smoke burning chamber 10.

In the case of certain insulating materials, such as P.V.C., or in ca:ethe furnace becomes accidentally overloaded, a second smoke burningchamber may be provided. This second smoke burning chamber 30, FIG- URE4, may be mounted above and be independent of the first smoke burningchamber 10. As shown in FIG- URE 4 this second smoke burning chamber 30is connected to the chimney 16 by means of two gas ducts, one of saidgas ducts 31 acting as a smoke inlet from the chimney 16 into saidsecond smoke burning chamber 30 and the other gas duct 32 acting as asmoke outlet from said second smoke burning chamber 30 into the chimney.This second smoke burning chamber 30 is also provided with the one ormore oil or gas fired burners 33 of the kind already described withreference to burners 6 and 11. As will be seen from FIGURE 4 the secondsmoke burning chamber 30 includes a bridge wall 34 that projects intothe chamber 30 to ensure that the smoke entering via the gas duct 31shall pass the one or more burners 33 before escaping via the gas duct32. An air ducting 35 receives air from the suction fan 26.

Indicated diagrammatically in FIGURE 4 is a motorised damper 36 thatextends across the chimney 16 between the gas ducts 31 and 32, whichdamper 36 is normally in its open position. Also shown diagrammaticallyin FIGURE 4 is a motorised damper 37 extending across the gas duct 31,the damper 37 normally being in its closed setting. The operation of thesecond smoke burning chamber 30 can be made automatic by connecting thecontrols 38, 39 for the dampers 36 and 3-7 to the photo-electric smokewarning device 52 already referred to. Operation of the photo-electricsmoke warning device causes the control 38 to close the damper 36 andthe control 39 to open the damper 37 thereby diverting the smoke risingup the chimney 16 through the second smoke burning chamber 30 to beburnt by the one or more burners 33 before escaping up the chimney, thephoto-electric smoke warning device bringing the one or more burners 33and the flow of air through the ducting 35 into operation during thisperiod. Alternatively the photo-electric smoke warning device can beused to operate a flashing light and/ or a bell, as already stated, toindicate that the smoke obscurity is beyond 50% and to indicate to theoperators of the furnaces that the dampers 36 and 37 of the furnace mustbe manually operated to divett the smoke rising in the chimney 16 intothe second smoke burning chamber 30.

When dealing with cables covered with P.V.C. there are, as alreadystated, numerous chemical gases to be eliminated, such as Phosgene, andHCl, these gases being produced by the burning of the P.V.C. Toeliminate these gases the furnace may be associated with a gas coolingand scrubbing plant of any suitable known form. Such plant may beconnected to the furnace, for example below the damper 17 shown inFIGURE 1 so that when the damper 17 is closed the gases rising up thechimney 16 are forced to pass through said cooling and scrubbing plant.

As shown in the particular embodiment illustrated in FIGURE 5 a ducting40 is coupled to the chimney 16 at a point below a damper 41 extendingacross the chimney 16. The ducting 40 leads to the top of a coolingtower 42 containing a number of sprays that are supplied with water viaa pipe 43, there being also a pipe 44 connected to the cooling tower 42said pipe 44 being used to supply a dilute solution of caustic soda to ajet at the top of the cooling tower.

The cooled gases are conveyed from the bottom of the cooling tower 42 toa gas washer 45 having a drain cock 46. Finally, an extractor fan 47removes the purified gases from the gas washer 45 and directs them intoan exhaust stack 48, preferably fibre glass lined, for discharge toatmosphere. A motorised or manually controlled damper 49 is included inthe ducting 40 so that the cooling and scrubbing plant can be shut offfrom the chimney 16 when not required, under which conditions the damper41 will be opened.

The above described gas cooling and scrubbing plant is by way of exampleonly and any other suitable cooling and scrubbing plant may besubstituted therefor.

Having now described one particular embodiment of the invention it willbe appreciated that many modifications thereof are possible as may fallwithin the scope of the appended claims.

Thus, for example, although only one air inlet 7 has been shown on eachside of the hearth there may be a plurality of such air inlets at spaceddistances apart along the hearth.

Also, whereas the suction fan 26 has been described as taking its entireair supply from the cowling 25 it will be appreciated that such a fancan take an additional supply of air from some other additional positionshould this be deemed desirable.

Also, whereas the burners 6 and 11 have been shown as being disposed inthe side walls of the furnace such burners may be replaced by, orsupplemented by, burners situated in the roof 4 and in the top 9 of thesmoke burning chamber 10.

The fuel supply lines to the burners 6 and 11 have not been shown inFIGURE 2 since these may be arranged in any convenient manner.

It will -be appreciated that the furnace can be used to deal withmaterials other than electric cables and the like and that these havebeen quoted by way of example only.

It is also within the scope of the present invention to provide twofurnaces arranged as a single operative unit in a side-by-siderelationship in order to provide a unit having double the capacity of asingle unit. The advantage of such a construction is that for doublecapacity, the two furnaces can share a common cowling 25 extendingacross the door of each furnace, and further economy can be effected byutilising a single suction fan 26 to supply air to the furnaces. Also,if desired, one final outlet chimney may be provided.

If a scrubbing plant is associated with such a unit, further economy canbe effected since the scrubbing plant will not be very much larger fortwo furnaces than for one.

With two furnaces arranged as a single operative unit, the unit can bemore effectively operated if one unit is used for running of lead fromwaste cables and the like whilst the other furnace is used for burningoff rubber since the final gases passing up a common outlet chimneywould then be less intense, as smoke, than the gases produced by asingle furnace burning off rubber, the reason for this being, of course,that the practically smokeless gases from the furnace running off leadwill mix with the gases escaping from the furnace burning off rubberbefore passing up a common outlet chimney. Similar considerations applyif one furnace is used for burning off a mixture of goods, some of whichincorporate P.V.C., and the other furnace is used for running off leador burning off rubber since the resulting mixture of gases passing up acommon chimney would then contain a smaller percentage of poisonousgases as produced by the P.V.C. goods than a single furnace burning offP.V.C.

Operation of the two furnaces in this manner can result in theelimination of the scrubber plant if too great a concentration of P.V.C.is not present in the one furnace.

What I claim is:

1. A furnace for burning insulation off of cables and for recoveringmetal from such cables comprising:

a hearth sloping downwardly towards the front of the furnace;

front and side walls and a roof extending over and along said hearth tothereby define a first burning chamber;

first burner means in said burning chamber for generating heat to burninsulation off of cables placed therein;

a bridge wall extending upwardly and running transversely across therear of said hearth, said bridge wall terminating below the level of thefirst burning chamber roof to thereby define a flue opening;

said flue leading to a smoke burning chamber disposed behind and abovesaid hearth, said smoke burning chamber having a roof at a higherelevation than that of the first burning chamber roof;

second burner means in said smoke burning chamber for burning the smokeand gases located therein;

an outlet to a chimney from said smoke burning chamber located below thelevel of the top of said bridge wall;

a photoelectric smoke warning device mounted at the outlet of said smokeburning chamber to trigger a flashing light and bell to indicate whenthe furnace is overloaded and is creating excess fumes and smoke;

and a second smoke burning chamber located adjacent said chimney anddownstream from said first smoke burning chamber outlet, said secondsmoke burning chamber including an inlet duct through which smoke fromsaid chimney may enter, third burner means, and an outlet duct throughwhich smoke returns to said chimney, said inlet and outlet ducts beingprovided with motor-operated dampers connected to and controlled by saidphoto-electric smoke warning device, whereby said inlet and outlet ductsare opened to permit said second smoke-burning chamber to function onlywhen the unburned gas and smoke content of said chimney exceeds apre-selected limit,

References Cited UNITED STATES PATENTS 2,051,463 8/193 6 Barker 266-402,729,301 1/1956 Ekstrom 26631 X 2,832,585 4/1958 Hansen 26631 2,964,30412/1960 Rice 2663l X 2,995,354 8/1961 Tunder et al 266-31 3,129,9324/1964 Richaud 26327 3,190,747 6/1965 Namy et al 26631 X 3,271,1349/1966 Derham 26633 X J. SPENCER OVERHOLSER, Primary Examiner. E. MAR,Assistant Examiner.

